1. Field of the Invention
The present invention relates to a label for use in in-mold molding in which the label is initially set in a mold so that the side of the label which is in contact with the mold wall surface contains printed matter, and a parison of a molten thermoplastic resin is introduced into the mold and molded by blow molding or a molten thermoplastic resin sheet is molded in the mold by vacuum forming or air pressure forming to produce a labeled container.
2. Discussion of the Background
A conventional integral molding process for producing a labeled resin container comprises inserting a blank or a label in a mold and then molding a container by injection molding, blow molding, differential pressure molding, foam molding, etc., to decorate the container within the mold (see JP-A-58-69015 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) and EP-A-254923). Such known in-mold labels include gravure printed resin films, multicolor offset printed synthetic papers (see, for example, JP-B-2-78 14 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) and JP-A-2-843 19), and gravure printed aluminum labels comprising an aluminum foil laminated on the back side thereof with high pressure low density polyethylene and an ethylene/vinyl acetate copolymer.
However, the process for producing containers decorated with the aforementioned in-mold labels or blanks through in-mold molding has the following problem. When labels are fed to a mold using an automatic label feeder especially in a low humidity atmosphere as in winter, electrostatic charges which have built up in the stack of labels are not removed and two or more labels are erroneously fed simultaneously to the mold, if the labels have insufficient antistatic properties. As a result, containers having a label adhered thereto in an improper position, i.e., rejects, are produced and the labels are not effectively utilized.
Another problem is that in a label production process the film or synthetic paper comes to have poor suitability for feeding and discharge in printing thereon especially by offset printing and, as a result, the label production machine has to be stopped and restarted many times.
Proposed for eliminating such problems are: an in-mold label having a heat sealable resin layer made of an ethylene resin containing a low-molecular weight antistatic agent of the kneading type, e.g., sorbitan monooleate or glycerol monostearate; and an in-mold label having an antistatic film formed by coating the surface of a heat sealable ethylene resin layer with a low-molecular weight antistatic agent, e.g., a poly(oxyethylene) derivative, and then drying the coating.
However, both in-mold labels have a drawback in that the antistatic properties do not last for long. Furthermore, the former in-mold label has another problem. That is, the antistatic agent migrates to and accumulate on the surface of the heat sealable resin layer to thereby significantly impair the fusion bondability of the heat- sealable resin to containers. As a result, reject containers are produced in which the labels have not been fusion-bonded to the containers at all or the labels adhered to the containers have blisters.
An object of the present invention is to provide an in-mold label having excellent suitability for label feeding and discharge and capable of producing a labeled container in which the label applied has no blister and has been fusion-bonded to the container at a high strength.
The present invention provides an in-mold label comprising a thermoplastic resin film base layer (I) carrying printed matter on its front side and a heat sealable resin layer (II) formed on the back side of the base layer (I), said heat sealable resin layer (II) being made of a resin composition comprising:
The in-mold label can have satisfactory suitability for insertion into molds (suitability for label feeding and discharge) and be tenaciously fusion-bonded to container main bodies by incorporating a polyetheresteramide (b), which retains long-lasting antistatic properties and is nontacky, into the heat sealable resin layer (II) and optionally further incorporating a polyamide resin (c) thereinto.